scholarly journals Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 429 ◽  
Author(s):  
Roberto Tascioni ◽  
Luca Cioccolanti ◽  
Luca Del Zotto ◽  
Emanuele Habib
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Winter Season ◽  
Electric Energy ◽  
Combined Heat And Power ◽  
Heat Transfer Fluid ◽  
Energy Output ◽  
Small Scale ◽  
Longitudinal Model ◽  
Lumped Model

In this paper four different detailed models of pipelines are proposed and compared to assess the thermal losses in small-scale concentrated solar combined heat and power plants. Indeed, previous numerical analyses carried out by some of the authors have revealed the high impact of pipelines on the performance of these plants because of their thermal inertia. Hence, in this work the proposed models are firstly compared to each other for varying temperature increase and mass flow rate. Such comparison shows that the one-dimensional (1D) longitudinal model is in good agreement with the results of the more detailed two-dimensional (2D) model at any temperature gradient for heat transfer fluid velocities higher than 0.1 m/s whilst the lumped model agrees only at velocities higher than 1 m/s. Then, the 1D longitudinal model is implemented in a quasi-steady-state Simulink model of an innovative microscale concentrated solar combined heat and power plant and its performances evaluated. Compared to the results obtained using the Simscape library model of the tube, the performances of the plant show appreciable discrepancies during the winter season. Indeed, whenever the longitudinal thermal gradient of the fluid inside the pipeline is high (as at part-load conditions in winter season), the lumped model becomes inaccurate with more than 20% of deviation of the thermal losses and 30% of the organic Rankine cycle (ORC) electric energy output with respect to the 1D longitudinal model. Therefore, the analysis proves that an hybrid model able to switch from a 1D longitudinal model to a zero-dimensional (0D) model with delay based on the fluid flow rate is recommended to obtain results accurate enough whilst limiting the computational efforts.

scholarly journals Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM

2019 ◽  
Vol 3 (4) ◽  
pp. 88 ◽  
Author(s):  
Maria K. Koukou ◽  
George Dogkas ◽  
Michail Gr. Vrachopoulos ◽  
John Konstantaras ◽  
Christos Pagkalos ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Behavior ◽  
Latent Heat ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Solidification Processes

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished.

Influence of Measurement Equipment on the Uncertainty of Performance Data from Test Loops for Concentrating Solar Collectors

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Nicole Janotte ◽  
Eckhard Lüpfert ◽  
Robert Pitz-Paal ◽  
Klaus Pottler ◽  
Markus Eck ◽  
...  
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Performance Testing ◽  
Volumetric Flow Rate ◽  
Heat Transfer Fluid ◽  
Individual Measurement ◽  
Uncertainty Range ◽  
Direct Normal Irradiance ◽  
Measurement Uncertainties ◽  
The Individual

Parabolic trough concentrating collectors play a major role in the energy efficiency and economics of concentrating solar power plants. Therefore, existing collector systems are constantly enhanced and new types were developed. Thermal performance testing is one step generally required in the course of their testing and qualification. For outdoor tests of prototypes, a heat transfer fluid loop (single collector or entire loop) needs to be equipped with measurement sensors for inlet, outlet, and ambient temperature as well as irradiance, wind speed, and mass or volumetric flow rate to evaluate the heat balance. Assessing the individual measurement uncertainties and their impact on the combined uncertainty of the desired measurement quantity one obtains the significance of the testing results. The method has been applied to a set of EuroTrough collector tests performed at Plataforma Solar de Almería, Spain. Test results include the uncertainty range of the resulting modeling function and exemplify the effects of sensors and their specifications on the parameters leading to an uncertainty of ±1.7% points for the optical collector efficiency. The measurement uncertainties of direct normal irradiance and mass flow rate are identified as determining uncertainty contributions and indicate room for improvement. Extended multiple sensor deployment and improved calibration procedures are the key to further reducing measurement uncertainty and hence increasing testing significance.

scholarly journals An Ultrasonic-Capacitive System for Online Characterization of Fuel Oils in Thermal Power Plants

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7979
Author(s):  
Mateus Mendes Campos ◽  
Luiz Eduardo Borges-da-Silva ◽  
Daniel de Almeida Arantes ◽  
Carlos Eduardo Teixeira ◽  
Erik Leandro Bonaldi ◽  
...  
Keyword(s):  
Flow Rate ◽  
Total Mass ◽  
Power Plants ◽  
Thermal Power ◽  
Electric Energy ◽  
Thermal Power Plants ◽  
Heating Value ◽  
Fuel Oils

This paper presents a ultrasonic-capacitive system for online analysis of the quality of fuel oils (FO), which are widely used to produce electric energy in Thermal Power Plants (TPP) due to their elevated heating value. The heating value, in turn, is linked to the quality of the fuel (i.e., the density and the amount of contaminants, such as water). Therefore, the analysis of the quality is of great importance for TPPs, either in order to avoid a decrease in generated power or in order to avoid damage to the TPP equipment. The proposed system is composed of two main strategies: a capacitive system (in order to estimate the water content in the fuel) and an ultrasonic system (in order to estimate the density). The conjunction of the two strategies is used in order to estimate the heating value of the fuel, online, as it passes through the pipeline and is an important tool for the TPP in order to detect counterfeit fuel. In addition, the ultrasonic system allows the estimation of the flow rate through the pipeline, hence estimating the amount of oil transferred and obtaining the total mass transferred as a feature of the system. Experimental results are provided for both sensors installed in a TPP in Brazil.

Biomass from agriculture in small-scale combined heat and power plants – A comparative life cycle assessment

2011 ◽  
Vol 35 (4) ◽  
pp. 1572-1581 ◽  
Author(s):  
M. Kimming ◽  
C. Sundberg ◽  
Å. Nordberg ◽  
A. Baky ◽  
S. Bernesson ◽  
...  
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Power Plants ◽  
Combined Heat And Power ◽  
Small Scale ◽  
Comparative Life Cycle Assessment

scholarly journals The Operating Strategies of Small-Scale Combined Heat and Power Plants in Liberalized Power Markets

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3110 ◽  
Author(s):  
Pavel Atănăsoae
Keyword(s):  
Electricity Markets ◽  
Electricity Market ◽  
Power Plants ◽  
High Efficiency ◽  
Organic Rankine Cycle ◽  
Combined Heat And Power ◽  
Operating Conditions ◽  
Power Markets ◽  
Small Scale ◽  
Operating Strategies

Distributed generation is a good option for future energy systems with respect to sustainable development. In this context, the small-scale combined heat and power (CHP) plants are seen as an efficient way to reduce greenhouse gas emissions due to lower fuel consumption compared to the separate generation of the heat and electricity. The objective of this paper is to establish operating strategies of the small-scale CHP plants to reduce operational cost and increase revenue in liberalized electricity markets. It analyzes a cogeneration plant with organic Rankine cycle and biomass fuel under the conditions of the Romanian electricity market and the green certificates support scheme for electricity generated in high efficiency cogeneration and from renewable sources. The main finding is that choosing an appropriate mode of operation and using correlated prices of heat and electricity can increase the trading profitability of a CHP plant in liberalized power markets. This can be done by an analysis of the particularities and the specific operating conditions of the CHP plant. The results show that the operating strategies of the CHP plant can yield substantial net revenues from electricity and heat sales. The CHP plant can be economically operated to a useful heat load of more than 40% when operating strategies are applied.

scholarly journals Validation of the operation efficiency criteria for geothermal probes in flooded mine workings

2020 ◽  
pp. 100-105
Author(s):  
D. V Rudakov ◽  
O. V Inkin
Keyword(s):  
Heat Transfer ◽  
Energy Balance ◽  
Flow Rate ◽  
Cost Efficiency ◽  
Net Present Value ◽  
Electric Energy ◽  
Heat Transfer Fluid ◽  
Geothermal System ◽  
Geothermal Systems ◽  
Operation Efficiency

Purpose. To develop and test the energy and cost criteria for evaluating the operation efficiency of a closed geothermal system using coaxial or U-shaped probes that can be installed in flooded workings of mines. Methodology. To justify the energy and cost criteria, we applied thermodynamic, hydraulic and cost-efficiency relationships, conducted the engineering analysis of closed geothermal systems, studied hydrogeological settings and geothermal conditions of the mines of the Selidovo group in Donbas. The developed criteria were examined within the ranges of key parameters such as the flow rate of the heat transfer fluid and the probe submerged length. Findings. We quantified the influence of the probe submerged length and the heat transfer fluid flow rate on the energy balance and the net present value NPV and identified the parameter combinations that allow achieving efficient heat recovery in terms of energy balance and cost-efficiency. The produced/spent energy ratio may reach 1.52.2 and the NPV a few dozen thousand when increasing the submerged depth to 500 m at the flow rate of 20m3/d. A higher flow rate may lead to a negative energy balance but the NPV remains positive within some ranges of the probe submerged length, thus, indicating the system profitability. The payback period can be shortened to a few years. Originality. The proposed energy criterion balances the thermal energy produced and the thermal equivalent of electric energy generated using fossil fuel and spent on system operation. This ratio as distinct from the usually applied COP parameter allows comparing the energies of the same nature and drawing more adequate conclusions on environmental acceptability of a geothermal system. Practical value. The proposed criteria can be used for prioritization of geothermal system installation and the operation efficiency evaluation among the number of potential sites in post mining areas.

Thermal/electric energy generation and CO2 production for greenhouse facilities

2019 ◽  
Vol 2 (3) ◽  
pp. 141-151
Author(s):  
O. E. Gnezdova ◽  
E. S. Chugunkova
Keyword(s):  
Carbon Dioxide ◽  
Power Distribution ◽  
Power Plants ◽  
Electric Energy ◽  
Electricity Consumption ◽  
Vegetable Crops ◽  
Carbon Dioxide Injection ◽  
Electricity Rates ◽  
Traditional Patterns ◽  
Generation Power

Introduction: greenhouses need microclimate control systems to grow agricultural crops. The method of carbon dioxide injection, which is currently used by agricultural companies, causes particular problems. Co-generation power plants may boost the greenhouse efficiency, as they are capable of producing electric energy, heat and cold, as well as carbon dioxide designated for greenhouse plants.Methods: the co-authors provide their estimates of the future gas/electricity rates growth in the short term; they have made a breakdown of the costs of greenhouse products, and they have also compiled the diagrams describing electricity consumption in case of traditional and non-traditional patterns of power supply; they also provide a power distribution pattern typical for greenhouse businesses, as well as the structure and the principle of operation of a co-generation unit used by a greenhouse facility.Results and discussion: the co-authors highlight the strengths of co-generation units used by greenhouse facilities. They have also identified the biological features of carbon dioxide generation and consumption, and they have listed the consequences of using carbon dioxide to enrich vegetable crops.Conclusion: the co-authors have formulated the expediency of using co-generation power plants as part of power generation facilities that serve greenhouses.

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